Laser beam device with apertured reflective element

ABSTRACT

A multi-beam tool is disclosed which can perform square, plumb, and level function which may be required in a construction environment. The tool can generate in a preferred embodiment up to five orthogonal beams with two beams being plumb and three beams being leveled. Combinations of two level beams, or a level and a plumb beam in orthogonal arrangement can produce a square alignment set of beams. The tool includes in a preferred arrangement a self-leveling pendulum to which a laser and quad-mirror arrangement is secured. The self-leveling pendulum is damped in order to allow the tool to settle down and provide alignment after the tool is positioned as desired. The quad-mirror, the magnetic damping, and the coiled wire allowing power to be provided to the laser assembly, each separately, and also in combination, provide for a compact tool.

CROSS-REFERENCE

The herein application claims the benefit of U.S. ProvisionalApplication No. 60/134,403, filed May 17, 1999, entitled SELF-LEVELINGPENTA LASER BEAM DEVICE, and U.S. Provisional Application No.60/159,524, filed Oct. 15, 1999, entitled SELF-LEVELING PENTA LASER BEAMDEVICE. Both of these applications are incorporated herein by reference.

Reference is made to U.S. Pat. No. 5,680,208, issued Oct. 21, 1997,entitled GRAVITY ORIENTED LASER SCANNER, which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

In many instances it is desired to establish reference lines. This isparticularly useful for construction, grading, and “do it yourself”activities. Traditional tools for these tasks include straight edges,rulers, protractors, squares, levels, and plumb bobs. More modern toolsinclude laser alignment devices.

Laser alignment devices include simple pointers, pointers with a bubblevial, self-leveling pointers, multiple beam pointers, and devices thatproduce a sheet of light. It is highly desirable to have multiple beamsthat are mutually orthogonal. This is typically achieved by severalpartially silvered mirrors at 45 degrees to the laser beam. This methodrequires placing the mirrors in precise alignment and securing them withglue. Further, the mirrors should be extremely stable over time andtemperature. More beams require more mirrors at added expense andcomplexity.

SUMMARY OF THE INVENTION

The present invention relates to improvements to this field renderingsimpler, more stable and cost effective laser devices which can generateone or more laser beams for measuring, aligning, leveling and otherpurposes.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of an embodiment of a penta beam splitterof the invention.

FIG. 2 is a perspective view of another embodiment of a beam splitter ofthe invention.

FIG. 3 is a further embodiment of the invention which can be used toproject a pattern such as a pattern of cross hairs.

FIGS. 4a and 4 b are perspective and side sectional views of yet anotherembodiment of the invention that allows for steering beams which are atangles with respect to the main laser source.

FIG. 5 is a side sectional view of yet another embodiment of theinvention wherein the main laser beam can be focused by symmetricalcrimping of the housing of the embodiment.

FIGS. 6a and 6 b depict side sectional views of another embodiment ofthe invention, showing how the laser assembly is suspended by a bearingmount.

FIG. 7 is a perspective view of another embodiment of the inventionusing elliptical reflective mirrors.

FIG. 8 depicts an interference target resulting from the use of deviceof FIG. 7.

FIG. 9 is a perspective view of another embodiment of the inventionusing square reflective mirrors.

FIGS. 10a and 10 b depict interference targets resulting from use of thedevice of FIG. 9.

FIG. 11 is a perspective view of another embodiment of the inventionusing rectangular mirrors.

FIGS. 12a, 12 b, 12 c depict interference targets resulting from use ofthe device of FIG. 11.

FIG. 13 is a side view of a pendulum laser mount with springcompensation.

FIG. 14 is a side view similar to FIG. 13 which allows for fieldcalibrations.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

I. Penta Beam Splitter

The present invention (FIG. 1) achieves the much-desired feature ofproducing a series of mutually orthogonal beams with a single splitter.Further, the beams are mutually coincident, that is, the beams allemanate from the same point.

The splitter in this embodiment is fabricated from a small block orcylinder of aluminum 2. Other materials and fabrication techniques canbe otherwise employed. Four reflective mirror surfaces 8 a-8 d areproduced by a process known as “single point diamond turning”. Thisprocess is widely used to produce polygonal mirrors for laser printers.In one particular embodiment of the invention, four sections or portions10 a-10 d of the collimated beam 9 are reflected from the mirrorsurfaces. A fifth portion of the light 12 passes directly through a hole14 in the center of the block.

The angle of the mirrors must be precisely 45 degrees to the incidentbeam and have precise rotational symmetry. This is readily achieved byoptical tooling fixtures.

In this embodiment, light from laser diode 4 is directed through a lensand collimator 6. This collimated light is directed at mirror block 2.

In another embodiment, a similar effect could be achieved by use of arefractive device that employs total internal reflection or refractionto produce a 90 degree bend. A small flat portion is created on the tipof the device closest to the incoming beam to allow part of the beam topass through undeflected, producing a fifth beam.

II. Beam and Disk Splitter

A related feature can be achieved by using a conical surface 16 and hole14 as depicted in the embodiment of FIG. 2. This produces a plane ordisk of laser light 18, together with an orthogonal laser spot.

Various embodiments of the invention may include a multiple facetedreflective device or devices having a mix of cylindrical and facetedareas. For example, a device having twenty-four facets would yield 24beams or spots, each separated from its nearest neighbor by an angle of15 degrees. Larger areas could be used for four of the facets, whichwould make those four reflected beams brighter relative to the others.This is useful in marking the major axes.

III. Cross Hair Projection

At short distances the beam may be too bright to use to easily centerupon a reference line or point. In an embodiment of the invention asdepicted in FIG. 3, a masking element such as a holographic film 24,positioned on one or more of the laterally reflected beams 22 (or beams10 a, b, c, d of FIG. 1) can be used to project a more useful shortrange image such as a cross hair 28, or a series of concentric circles.An aperture 26 in the mask allows some light to pass through to be usedat a distance.

Alternatively, in other embodiments, a similar effect may be achieved byintroducing intentional imperfections into the mirror surface.

FIG. 3 is simplified by using a half-silvered mirror as a beam splitter.Alternatively, the beam splitting FIG. 1 could be used.

IV. Side Beam Steering

The four side beams produced by the embodiment of a penta beam splitterof FIG. 1 are by design mutually perpendicular and coplanar, theaccuracy of which being determined by the accuracy of the cuttingprocess. But they may be thereafter aligned or adjusted to be preciselyperpendicular to the central beam. A traditional approach would employ 4set screws to precisely deflect the mirror block.

A present embodiment of the invention (FIGS. 4a, 4 b) utilizes a novelapproach to beam adjustment in mounting the laser assembly within acylindrical enclosure 30 of deformable material, for example metal orplastic. The enclosure contains a series of beam exit holes 36 a-36 daround its circumference to allow the reflected beams exit the device. Aweb of deformable material remains between the holes. The method of beamsteering as embodied in the invention works by crimping the web 34formed between the side exit holes. Deforming an adjacent pair of websslightly shortens the cylindrical structure in that local region. Thiscauses the beam to rotate back about this location. Crimping andadjustment of the beam direction are noted by the angle θ in FIG. 4a.

This method of beam adjusting has the significant benefit of eliminatingthe need for glue, which aids in manufacturing and long term stability.

V. Beam Focus by Symmetric Crimping

A technique similar to that of side beam steering described above may beemployed to focus the laser diode, as shown in the embodiment of FIG. 5.In this embodiment another series of holes 38 a-38 d (holes 38 c and 38d are not shown as they are in the cut-away half of the enclosure) areintroduced into the cylindrical enclosure, this time between the lasersource 4 and the lens 6. A web 39 of material remains between the holes.Bending all four webs the same amount causes the overall length of thesection to shorten. In practice, the diode may be pressed into thecylinder at a distance just longer than nominal focal distance, andcrimping applied to shorten the diode/lens separation by an amount 40until the laser comes into focus. Typically, many metals have somerebound after bending. This factor can be predicted and compensated forby crimping past the focus point.

VI. Bearing Mount

A traditional means of producing a quality gimbal is with two pairs ofroller bearings. The pairs must be precisely located and a preload mustbe applied to take out the clearance between the bearings and races. Anembodiment of the present invention (FIGS. 6a, 6 b) reduces this to asingle pair of bearings 47, 48 suspended in a chain-like configuration.The slight angle θ shown on the transverse beam 46 allows the weight ofthe pendulum 49, on which the laser enclosure 30 is mounted, to bedistributed over both bearing units.

The pendulum arrangement shown in FIGS. 6a and 6 b is hung from thedouble bearings 47, 48, and includes pendulum 49. Pendulum 49 mounts thelaser enclosure 40 which can include the laser enclosure depicted inFIGS. 1 and 2 by way of example. The enclosure of FIG. 1 with thequad-mirror is preferable. Still preferable, as is described more fullyhereinbelow would be the quad-mirror shown in FIG. 9 or 11.

FIG. 6a is a cross-sectional view of the upper bearing 47 shown in FIG.6b. The lower bearing 48 is mounted on a pin 46 which extends at anangle from the pendulum body 49. It is in this way that the lowerbearings 48 hangs down from the upper bearings 47, and the pendulum 49hangs down from the lower bearings 48. At the base of the pendulum isthe damping weight 44. The damping weight 44 is generally comprised of aconductor and in particular, a copper conductor. In order for dampeningto occur, a magnet arrangement 45 is depicted. In a preferredembodiment, the magnet arrangement includes a soft iron horseshoe-shapedmount 66 which extends around the back side of the damping weight 44.Two magnets, such as magnet 51, are mounted at the ends of the horseshoe66. The horseshoe provides a return path for the magnetic flux in orderto assist and concentrating the magnetic field between the front facesof the magnets 51 in order to more efficiently damp the damping weight44. It is to be understood that in a preferred embodiment, a magneticarrangement of 45 would be placed on each side of the damping weight.The damping weight would swing through the arrangements and be damped byboth magnetic arrangements 45.

VII. Round Mirrors 54

The shape of the laser spot is of considerable interest. The practicalneed is to be able to identify and mark the center of the spot. In asquaring or plumb application this needs to be done in two axes. Tofacilitate this, a natural choice is round spots. The followingdescribes a novel method of producing them. It involves die casting thequad mirror, previously described, in aluminum. A feature of the deviceis four small posts 56 a-56 d surrounding a central hole 58 (FIG. 7).The end of each post is single point diamond turned to produce fourelliptical mirrors. The axial projection of each mirror is a circle.Thus, they act as apertures to project circular shafts of light in eachof 4 directions.

Round Spots Resulting From Round Mirrors

The smaller the circular apertures 56 a-56 d, the larger the laser spotsappear at a distance. This is due to the normal dispersion of light offof a sharp aperture. Since the laser light is monochromatic, the wavefront from one side of the aperture interferes with the wave front fromthe other side. This results in a series of circular interference rings59 (FIG. 8). The exact size and diameter of the central spot 60 fromhole 58 and these rings 59 depends on the wavelength, distance to thetarget, and the aperture diameter. Apertures in the range of 2 mmproduce acceptable spots.

VIII. Square Mirrors 60

A novel alternative to the pyramidal mirror geometry proposed in theabove is to form four small mirrors into a quad-mirror arrangement 60with parallel sides (FIG. 9). This is readily accomplished by formingthe blank on a screw machine with a special profile for the end cone. Asquare aperture 64 is readily broached through the center. Four passesof a diamond-point fly-cutter then cuts four mirrors 62 a-62 b leavingthe conical section in-between. In use, this presents five similarapertures to the incident laser beam.

As can be seen in FIG. 9, the four mirrors meet each other at commoncorners which define the central square aperture 64. Corner 63 a, b, c,and d, at the sides of the four mirrors 62 a-62 d, do not go through theapex of the structure. In effect, the structure is truncated in order toform the square aperture 64. The truncated structure forms the squareaperture 64 from which the four mirrors 62 a-62 d emanate. Due to thisstructure, this arrangement provides appropriate interference pattern sothat targets can be formed as described below.

Square Spots

The square central aperture produces a nominally square spot (FIGS. 10a,10 b). As with the circular aperture, wave fronts from opposite sidesinterfere, but in this case a series of spots are formed radiating infour directions (FIG. 10a). This creates a “cross hair” formation thatis ideal for marking. The apertures formed by the mirrors perform in asimilar way. In the direction where parallel edges are presented,interference spots are formed. In the other direction, there is only onesharp edge (FIG. 10b). The dispersion from this edge produces a “smear”along this axis. It is similar in brightness and size to the string ofspots in the other direction. Thus a cross-hair appearance is produced.

IX. Rectangular Mirrors 68

The light from a laser diode is presented from a typical collimatinglens as a short line segment, in which the light is spread out morealong one cross-sectional axis than the other. In one embodiment, tobetter slice up this beam, the mirrors 70 a-70 b and 71 a-71 b need notbe all the same (FIG. 11). Of further design consideration is the powerdistribution desired. For example, the up and down beams may not bedesired to be as strong as the side beams, so the up and down reflectorsmay be designed to be smaller than the lateral or sideways reflectors. Awide range of power distributions is possible with minimal loss in theinter-mirror space.

With respect to FIG. 11, the configuration of the quad-mirror 68includes the following. The rectangular aperture 74 has four corners 75a-75 d. It is from these four corners that the mirrors 70 a, b, and 71a, b, extend. Thus, as previously indicated, the corners of the mirrorsdo not all originate from the same apex. Viewing mirror 71 a, it isevident that it is defined by substantially parallel side 72 a, b, whichoriginate respectfully from corner 75 a, 75 b. Similarly, thesubstantially parallel sides 73 a, 73 b of the mirror 70 b originatefrom corners 75 b, 75 c, respectively. This same pattern occurs for theother mirrors 70 a and 71 b. In such an arrangement, the cross-hairpatterns are created on the desired target. Also, as the sizes of themirrors can be made to have different areas, the intensity of the beamcan be made to vary.

Rectangular Spots

The spots (FIGS. 12a, 12 b, 12 c) produced by rectangular mirrors areapproximately rectangular. The direction of interference spots andsmears are similar to those described above with respect to squaremirrors. The spacing of the spots depends on the width of the aperturein each direction, so the spacing of the spots may not be the same foreach direction.

X. Spring Compensation

The embodiment of FIG. 13 includes a pendulum 80 which hangs down from agimble mount 76. The gimble mount allows the pendulum to swing in twodirections of freedom. Hanging down from the gimble mount is the coilwire 78 which is used to power the laser assembly 35. The laser assemblyincludes the driver board 41 to which the wire is attached. Hanging downfrom the pendulum is the damper 44. The damper 44 is damped by thedamping arrangement 45 as previously described.

The Laser Diode Optical assembly in enclosure 40 requires two electricalconnections. This is typically achieved by the use of very fine copperwires. But such wires present a surprisingly significant spring torqueon the pendulum. The nonzero stiffness has the property of dipping thebeam if the housing is rotated forward. This is one of the dominantlimiting factors in miniaturizing a pendulum assembly. Making thependulum longer, the service loop longer, and/or coiling the wires aretechniques widely used in existing system.

An embodiment of the invention has the wires formed into a coil 78 andused as an extension spring. Stretched across the axis of rotation ofthe pendulum 80 it functions as an “over center mechanism”. This has theinverse property that the beam pops up if the housing is tilted forward.

By carefully matching the bending stiffness against the over centerspring the two effects are largely canceled. Although FIG. 13 shows asectional view through one dimension, this effect works simultaneouslyin all degrees of freedom of the pendulum.

A further benefit of this method is that the over center spring acts torelieve gravitational drag torque on the bearings. This may make itpossible to use still shorter pendulums and rollerless bearings.

XI. Field Calibration by Spring Compensation

A feature of the invention is field calibration. This is typicallyaccomplished by adjusting screws 78 a, b, mounted in the pendulum. Inthe field, should the laser beams come out of alignment, the alignmentcan be corrected by adjusting the distribution of weight on thependulum. This is accomplished by adjusting the position of theadjusting screws 78 a, b, causing the screws to move into or out of thependulum.

Initial alignment during manufacturing can be accomplished by removingweight from the damper 44 by for example a drilling technique in orderto align the laser beams with preestablished targets.

With respect to another type of field alignment, the axial positioningof the over center spring is important. If off-axis it would leave a nettorque on the pendulum. A novel feature of invention allows for such amisalignment to be used to field calibrate the pendulum. As shown inFIG. 14, screw pairs 82, 84 can manipulate the spring mounting point 86,therein adjusting the orientation of the suspended laser assembly. Thishas the desirable property that the user need not come into contact withthe delicate pendulum assembly.

Industrial Applicability

The present invention provides for multiple embodiments which cangenerate multiple laser beams for measuring, aligning, leveling andother purposes. In addition, the embodiment are for beam steering andfocusing as well as mounting of the laser itself.

What is claimed is:
 1. A reflective element, comprising: a unitary bodyforming an axially directed aperture extending there-through, aplurality of reflective facets having a first reflectivity outward ofthe aperture and other sections having a second reflectivity in-betweenthe facets, each facet being obliquely oriented relative to the axialdirection.
 2. A reflective element, comprising: a unitary body formingan axially directed central aperture extending there-through, aplurality of reflective facets outward of the central aperture and othersections in-between the facets, each facet being obliquely orientedrelative to the axial direction, wherein the other sections are planarnon-reflective surfaces.
 3. The reflective element of claim 1, whereineach facet is oriented at 45 degrees relative to the axial direction. 4.The reflective element of claim 1, wherein the aperture has arectangular cross-section.
 5. The reflective element of claim 1, whereinthe aperture as a square cross-section.
 6. The reflective element ofclaim 1, wherein the aperture has a circular cross-section.
 7. Thereflective element of claim 1, wherein at least one of the facets issubstantially rectangular.
 8. The reflective element of claim 1, whereinat least one of the facets is substantially square.
 9. The reflectiveelement of claim 1, wherein at least one of the plural facets is largerthan at least one other of the plural facets.
 10. The reflective elementof claim 1, wherein the body forms four reflective facets having thefirst reflectivity and four other non-planar sections having the secondreflectivity in-between the four reflective facets.
 11. The reflectiveelement of claim 10, wherein the four facets are disposed at 45°relative to the axial direction and are substantially evenly disposed at90° intervals around an edge of the aperture.
 12. The reflective elementof claim 11, wherein two of the facets disposed on opposite sides of theaperture are larger than the other two facets.
 13. The reflectiveelement of claim 11, wherein substantially parallel facet edges definethe boundaries between each facet and the other sections adjacent toeach facet.
 14. The reflective element of claim 1, wherein the facetsare elliptical.
 15. The reflective element of claim 1, wherein the othersections are nonplanar sections.
 16. An optical tool, comprising: aunitary body forming an axially directed aperture extendingthere-through, a plurality of reflective facets having a firstreflectivity outward of the aperture and other sections having a secondreflectivity in-between the facets, each facet being obliquely orientedrelative to the axial direction; and a laser light source illuminatingthe reflective facets.
 17. The optical tool of claim 16, wherein thelight source is a laser diode.
 18. The optical tool of claim 17, furthercomprising a collimating lens disposed between the light source and theunitary body for directing a collimated beam of laser light at thereflective facets.
 19. The optical tool of claim 18, wherein the othersections are non-planar sections.
 20. The optical tool of claim 18,wherein each facet is oriented at 45 degrees to the axial direction. 21.The optical tool of claim 20, wherein the aperture has a rectangularcross-section.
 22. The optical tool of claim 20, wherein at least one ofthe facets is substantially rectangular.
 23. The optical tool of claim20, wherein the body forms four facets having the first reflectivity andfour other sections having the second reflectivity in-between the fourfacets.
 24. The optical tool of claim 23, wherein the four facets aresubstantially evenly disposed at 90° intervals around an edge of theaperture.
 25. The optical tool of claim 18, wherein substantiallyparallel facet edges define the boundaries between each reflective facetand the other sections adjacent to each facet.
 26. The optical tool ofclaim 18, wherein the facets are elliptical.
 27. A construction tool forproducing a plurality of light beams on intersecting lines, comprising:a light source providing a non-collimated beam of laser light; acollimating lens disposed to intercept and collimate less than theentire beam; and a unitary reflective element defining a centralaperture, at least two planar reflective surfaces having a firstreflectivity outward of the aperture, and other sections having a secondreflectivity outward of the aperture in-between the reflective surfaces,the normal to each reflective surface being oriented at 45° to thecollimated portion of the beam and 90° from the normal to the otherreflective surface when measured in a plane perpendicular to thecollimated beam, wherein the unitary reflective element is positioned inthe path of the collimated part of the beam to pass, without reflection,a center portion of the collimated beam through the central aperture andto reflect outer portions of the collimated beam from the reflectivesurfaces, the passed beam and at least two of the reflected beams beingmutually orthogonal.
 28. The tool of claim 27, wherein the reflectivesurfaces are elliptical.
 29. The tool of claim 27, wherein the othersections in-between the reflective surfaces are non-planar sections. 30.The tool of claim 27, wherein the light source is a diode laser.
 31. Thetool of claim 27, wherein the unitary reflective element defines atleast four reflective surfaces reflecting portions of the collimatedbeam along two orthogonal intersecting lines.
 32. The tool of claim 27,further comprising a conductive spring which provides power to the tool,and a pendulum, wherein the tool is hung from the pendulum.
 33. Anoptical tool, comprising: a unitary body forming an axially directedaperture extending there-through, a plurality of reflective facetsoutward of the central aperture, and other sections in-between thefacets, each facet being obliquely oriented relative to the axialdirection, wherein substantially parallel facet edges define theboundaries between each facet and the other in-between sections adjacentto each facet; and a laser light source illuminating the reflectivefacets with a laser beam, wherein the laser beam impinges across bothsubstantially parallel facet edges of at least one of the reflectivefacets.
 34. The optical tool of claim 33, wherein the light source is alaser diode.
 35. The optical tool of claim 34, further comprising acollimating lens disposed between the light source and the unitary bodyfor directing a collimated beam of laser light at the reflective facets.36. The optical tool of claim 35, wherein the other sections in-betweenthe facets are non-planar sections.
 37. The optical tool of claim 35,wherein each facet is oriented at 45 degrees to the axial direction. 38.The optical tool of claim 37, wherein the aperture has a rectangularcross-section.
 39. The optical tool of claim 37, wherein at least one ofthe facets is substantially rectangular.
 40. The optical tool of claim37, wherein the body forms four facets and four other sectionsin-between the four facets.
 41. The optical tool of claim 40, whereinthe four facets are substantially evenly disposed at 90° intervalsaround an edge of the aperture.
 42. The optical tool of claim 33,wherein the other sections in-between the facets comprise non-reflectivesurfaces.
 43. The optical tool of claim 33, wherein the facets have afirst reflectivity and the other sections in-between the facets have asecond reflectivity.
 44. The tool of claim 43, wherein the unitaryreflective element defines at least four reflective surfaces reflectingportions of the collimated beam along two orthogonal intersecting lines.45. A construction tool for producing a plurality of light beams onintersecting lines, comprising: a light source providing anon-collimated beam of laser light; a collimating lens disposed tointercept and collimate less than the entire beam; and a unitaryreflective element defining a central aperture, at least two planarreflective surfaces outward of the aperture, and other sections outwardof the aperture in-between the reflective surfaces, the normal to eachreflective surface being oriented at 45° to the collimated portion ofthe beam and 90° from the normal to the other reflective surface whenmeasured in a plane perpendicular to the collimated beam, whereinsubstantially parallel edges define the boundaries between eachreflective surface and the other in-between sections adjacent to eachreflective surface, and wherein the unitary reflective element ispositioned in the path of the collimated part of the beam to pass,without reflection, a center portion of the collimated beam through thecentral aperture and to reflect outer portions of the collimated beamfrom the reflective surfaces so that the passed and the at least tworeflected beams are mutually orthogonal, wherein the outer portions ofthe collimated beam impinge across both substantially parallel facetedges of at least one of the reflective surfaces.
 46. The tool of claim45, wherein the other sections in-between the reflective surfacescomprise non-reflective surfaces.
 47. The tool of claim 45, wherein thereflective surfaces have a first reflectivity and the other sectionsin-between the reflective surfaces have a second reflectivity.
 48. Thetool of claim 45, wherein the other sections in-between the reflectivesurfaces are non-planar sections.
 49. The tool of claim 45, wherein thelight source is a diode laser.